Combined sensor and bearing assembly

ABSTRACT

A combined sensor and bearing assembly including a rolling bearing unit and a rotation sensor unit. The rolling bearing unit is made up of a rotatable raceway member, a stationary raceway member and at least one row of rolling elements. The rotation sensor unit includes a to-be-detected member having a magnet and fitted to one of the raceway members, and a magnetic detecting member fitted to the other raceway member at a location confronting the to-be-detected member. This combined sensor and bearing assembly is used at a location close to an electromagnetic coil emanating a leakage magnetic field, in a condition in which a direction of flow of an electric current through the electromagnetic coil is fixed in one direction so that a direction of a magnetic flux, with which the magnetic detecting member is switched off, may coincide with a direction of the leakage magnetic flux.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 11/072,437filed Mar. 7, 2005 and claims the benefit of Japanese Application No.2004-063303, filed Mar. 8, 2004, in the Japanese Intellectual PropertyOffice, the disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a combined sensor and bearing assemblyfor detecting the revolution of a rotating element used in variousmachines and equipments, of a type having a point-of-origin signaldetecting capability that enables the detection of, for example, therotational speed of a rotary shaft.

2. Description of the Related Art

The combined sensor and bearing assembly capable of detecting therotational speed of one of inner and outer raceway members relative tothe other thereof is currently available in various types, one of whichis disclosed in, for example, the Japanese Laid-open Patent PublicationNo. 9-329614. However, it has been found that the rotation sensoremployed in those conventional combined sensor and bearing assemblies iscomplicated in structure and, therefore, attempts have been suggested toprovide the combined sensor and bearing assembly capable of detectingthe revolution through the detection of the point of origin, which willnow be discussed.

By way of example, the combined sensor and bearing assembly issuggested, in which a magnetic encoder having only a single magneticpolarity, for example, S-pole or only three magnetic polarities of N-,S- and N-poles at maximum in succession is mounted on the bearing innerrace, which is a rotatable raceway member, and, on the other hand, asingle magnetic sensor is mounted on the bearing outer race, which is astationary raceway member, in face-to-face relation with the magneticencoder. See, for example, the Japanese Patent Application No.2003-147511. According to this suggestion, the detection of the point oforigin (Z-phase) is possible and the rotational speed of the rotatableraceway member can also be detected.

The combined sensor and bearing assembly of the structure now suggestedis featured in compactness, elimination of the required adjustment inassemblage and robustness and is generally used for supporting, forexample, a machine drive motor.

Also, the magnetic encoder for the detection of the point of origin canbe obtained by securing a magnet, which has only one magnetic polarity,to a side surface of a sealing member. In such case, this sealing memberis concurrently used in the magnetic encoder and, therefore, thestructure can advantageously be simplified.

However, when the combined sensor and bearing assembly having thecapability of detecting the point-of-origin signal of the structurediscussed above is used in the vicinity of members such as, for example,an electric drive motor and an electromagnetic clutch tending togenerate a magnetic field, for detecting the rotational speed of arotary shaft, an Hall IC element forming the magnetic sensor may be kepton under the influence of a leakage magnetic flux at all times duringactivation of the electromagnetic clutch, resulting in incapability ofdetecting the rotational.

SUMMARY OF THE INVENTION

In view of the foregoing, the present invention is intended to providean improved combined sensor and bearing assembly, which is so structuredas to avoid the influence brought about by the leakage magnetic flux sothat the point of origin can be accurately detected even in theenvironment full of the leakage magnetic flux and without beingadversely affected by the leakage magnetic flux.

In order to accomplish the foregoing object of the present invention,one aspect of the present invention provides a combined sensor andbearing assembly having a capability of detecting a point of origin,which assembly includes a rolling bearing unit made up of a rotatableraceway member, a stationary raceway member and at least one row ofrolling elements rollingly interposed between the rotatable andstationary raceway members, and a rotation sensor unit including ato-be-detected member having a magnet fitted to one of the rotatable andstationary raceway members; and a magnetic detecting member fitted tothe other of the rotatable and stationary raceway members at a locationconfronting the to-be-detected member. This combined sensor and bearingassembly is used at a location close to an electric coil emanating aleakage magnetic field, in a condition in which a direction of flow ofan electric current through the coil is fixed in one direction so that adirection of a magnetic flux, with which the magnetic detecting memberis switched off, may coincide with a direction of the leakage magneticflux.

According to this aspect of the present invention, the magneticdetecting member can be switched off by the leakage magnetic field, butcan necessarily be switched on when the to-be-detected member is broughtin face-to-face relation with the magnetic detecting member. As such,even under the environment full of the leakage magnetic flux, the pointof origin can be accurately detected without being adversely affected bythe leakage magnetic flux.

The combined sensor and bearing assembly according to another aspect ofthe present invention, which is also provided herein, is featured inthat the combined sensor and bearing assembly is used at a locationclose to an electric coil emanating a leakage magnetic field, in such amanner that a direction of detection of a magnetic field by the magneticdetecting member crosses a direction of the leakage magnetic fluxinputted to the magnetic detecting member.

According to this different aspect of the present invention, since thecombined sensor and bearing assembly is used in such a manner that adirection of detection of a magnetic field by the magnetic detectingmember crosses a direction of the leakage magnetic flux inputted to themagnetic detecting member, the point of origin can be accuratelydetected without being adversely affected by the leakage magnetic flux.

In such case, the direction of detection of the magnetic field by themagnetic detecting member and the direction of the leakage magnetic fluxinputted to the magnetic detecting member may cross to each other at anangle of substantially 90°. Selection of this particular angle for thecrossing is effective to substantially eliminate the influence broughtabout by the leakage magnetic flux on the magnetic detecting member and,therefore, a further accurate detection of the point of origin ispossible.

In a preferred embodiment, the to-be-detected member may be a radialtype and the direction of detection of the magnetic flux by the magneticdetecting member may correspondingly be a radial direction. According tothis feature, when the combined sensor and bearing assembly of thepresent invention is used in, for example, a rotary support for anelectromagnetic clutch, and considering that the leakage magnetic fluxfrom the electromagnetic clutch develops in a direction axially of thebearing unit, the direction in which the magnetic detecting memberdetects the magnetic field can easily be set to cross the direction ofthe leakage magnetic flux.

In another preferred embodiment of the present invention, the rollingbearing unit may also include a sealing member having a reinforcementring made of a magnetic member, in which case a non-magnetic materialportion including the magnetic detecting member is mounted on agenerally L-sectioned ring member made of a magnetic material, with aradially extending portion of the ring member positioned close to and inparallel to the reinforcement ring of the sealing member.

According to this feature, since the leakage magnetic flux flows in theL-sectioned ring member after having bypassed, the magnetic leakagefield can easily flow in a radial direction between the rotatableraceway member and the stationary raceway member and, therefore, theleakage magnetic flux in the radial direction that is inputted to themagnetic detecting member can advantageously be reduced. For thisreason, it is possible to avoid the influence which may be brought bythe leakage magnetic flux on the magnetic detecting member, allowing anaccurate detection of the point of origin to be achieved.

In a further preferred embodiment, the rolling bearing unit may alsoinclude a sealing member having a reinforcement ring made of a magneticmaterial and further comprising a bypass ring made of a magneticmaterial positioned close to the reinforcement ring for reducing amagnetic resistance between the rotatable and stationary racewaymembers. The use of the bypass ring made of the magnetic material iseffective to reduce the magnetic resistance between the rotatableraceway member and the stationary raceway member, allowing the leakagemagnetic flux to concentrate on the bypass ring. For this reason, it ispossible to accomplish the detection of the point of origin without themagnetic detecting member being adversely affected by the leakagemagnetic flux.

The bypass ring referred to above may have a portion of itscircumference depleted to provide a cutout to thereby render the bypassring to represent a generally U-shape. In this case, the to-be-detectedmember and the magnetic detecting member are arranged within the cutout.This is particularly advantageous in that the to-be-detected member andthe magnetic detecting member can be positioned at the same axialposition in alignment with each other and, therefore, the rotationsensor unit can be assembled compact.

In a still further preferred embodiment of the present invention, themagnetic detecting member may have a magnetic detecting sensitivity solow that the leakage magnetic flux in the vicinity of the magneticdetecting member can not be detected. According to this feature, theinfluence which would be brought about by the leakage magnetic flux onthe magnetic detecting member can be minimized by the magnetic detectingsensitivity so that the magnetic detecting member can be switched ononly when the to-be-detected member is brought in face-to-face relationwith the magnetic detecting member. Also, in such case, regardless ofthe relation between the direction of magnetic detection by the magneticdetecting member and the direction of the leakage magnetic flux, theinfluence brought about by the leakage magnetic flux on the magneticdetecting member can advantageously be minimized.

In accordance with a further aspect of the present invention, there isprovided a combined sensor and bearing assembly having a capability ofdetecting a point of origin of the structure described above inconnection with the first and second mentioned aspects of the presentinvention, which is featured in that the combined sensor and bearingassembly is used at a location close to an electric coil emanating aleakage magnetic field and in that the magnet of the to-be-detectedmember is made up of an N-pole magnet and an S-pole magnet.

According to this further aspect of the present invention, during therelative revolution of the rotatable and stationary raceway members, themagnetic detecting member detects the N-pole magnet of theto-be-detected member to output a detected rotation signal in the formof a single train of pulses and also detects the S-pole magnet thereofto a detected rotation signal in the form of another train of pulses. Insuch case, even in a condition in which the magnetic detecting member iskept switched on by the leakage magnetic flux, depending on thedirection of the leakage magnetic flux, a period during which themagnetic detecting member is switched off occurs when one of the N-poleand S-pole is in position confronting the magnetic detecting member.Accordingly, even under the environment full of the leakage magneticflux, the detection of the point of origin and the concomitant detectionof the revolution can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more clearly understood from thefollowing description of preferred embodiments thereof, when taken inconjunction with the accompanying drawings. However, the embodiments andthe drawings are given only for the purpose of illustration andexplanation, and are not to be taken as limiting the scope of thepresent invention in any way whatsoever, which scope is to be determinedby the appended claims. In the accompanying drawings, like referencenumerals are used to denote like parts throughout the several views,and:

FIG. 1 is a fragmentary longitudinal sectional view of a combined sensorand bearing assembly according to a first preferred embodiment of thepresent invention;

FIG. 2 is a fragmentary end view, on an enlarged scale, of the combinedsensor and bearing assembly, showing a portion of a sealing memberemployed therein;

FIG. 3 is a fragmentary longitudinal sectional view an electromagneticclutch employing the combined sensor and bearing assembly according tothe present invention;

FIG. 4 is a fragmentary longitudinal sectional view, on an enlargedscale, of the electromagnetic clutch, showing an exemplary passage of aleakage magnetic flux towards the combined sensor and bearing assembly;

FIG. 5 is a fragmentary longitudinal sectional view, on an enlargedscale, of the electromagnetic clutch, showing an actual passage of aleakage magnetic flux towards the combined sensor and bearing assembly;

FIG. 6 is a fragmentary longitudinal sectional view of the combinedsensor and bearing assembly according to a second preferred embodimentof the present invention;

FIGS. 7 to 10 are fragmentary longitudinal sectional views of thecombined sensor and bearing assembly according to third to sixthpreferred embodiments of the present invention, respectively; and

FIGS. 11A and 11B illustrate pulse wave forms of a magnetic detectingmember.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the first place, reference is made to FIGS. 1 to 5 for the detaileddescription of a combined sensor and bearing assembly 1 according to afirst preferred embodiment of the present invention. In particular,FIGS. 1 and 2 illustrates the details of the combined sensor and bearingassembly 1 and FIG. 3 illustrates an electromagnetic clutch 3 employingthe combined sensor and bearing assembly 1.

As best shown in FIGS. 1 and 2, the combined sensor and bearing assembly1 includes a rolling bearing unit 6 made up of a rotatable racewaymember 4, a stationary raceway member 5 and two rows of rolling elements3 operatively retained by respective roller retainers 10 and rollinglyinterposed between the rotatable raceway member 4 and the stationaryraceway member 5 in a manner well known to those skilled in the art, anda rotation sensor unit 31. The rotatable raceway member 4 has an innerperipheral surface formed with inner raceway grooves 4 a and thestationary raceway member 5 has an outer peripheral surface formed withouter raceway grooves 5 a, wherefore the rows of the rolling elements 3are received in part within the inner raceway grooves 4 a and in partwithin the outer raceway grooves 5 a. An annular bearing space delimitedbetween the rotatable raceway member 4 and the stationary raceway member5 has its opposite open ends sealed off by respective annular sealingmembers 7.

In the illustrated embodiment, the rolling bearing unit 6 referred toabove is in the form of, for example, a dual row deep groove ballbearing having inner and outer races, which represent the stationary androtatable raceway members 5 and 4, respectively. Hence, so far showntherein, the outer race of the dual row deep groove ball bearing isrotatable relative to the inner race thereof.

The rotation sensor unit 31 includes a to-be-detected member 8 securedto the rotatable raceway member 4 and a magnetic detecting member 9secured to the stationary raceway member 5 at a location aligned withthe to-be-detected member 8 in a direction axially of the rollingbearing unit 6. In the instance as shown, the to-be-detected member 8and the magnetic detecting member 9 altogether form the rotation sensorunit 31 of an axial type, in which the to-be-detected member 8 and themagnetic detecting member 9 confront with each other in a directionaxially of the bearing assembly 1.

The to-be-detected member 8 is so magnetized axially that only when theto-be-detected member 8 is brought into the proximity of the magneticdetecting member 9, the latter can be switched on. More specifically, asbest shown in FIG. 2 in a fragmentary end view, the to-be-detectedmember 8 is in the form of a column-shaped or sheet-like magnetmagnetized to one of the annular sealing members 7 that is positionedadjacent the magnetic detecting member 9 (which sealing member ishereinafter referred to as the right sealing member). Thisto-be-detected member 8 has one of its opposite surfaces confronting themagnetic detecting member 9, which is magnetized to only one polarity,i.e., S-pole or a maximum number of three alternating polarities, i.e.,N-, S- and N-poles deployed successively in a directioncircumferentially of the right sealing member 7. Securement of themagnet forming the to-be-detected member 8 to the right sealing member 7may be carried out either by bonding the magnet to a reinforcement ring11 of the right sealing member 7, or by embedding the magnet through aninsert molding technique when a rubber member 32 is bonded byvulcanization to the reinforcement ring 11.

With the to-be-detected member 8 so structured as hereinabove described,when the S-pole approaches the magnetic detecting member 9, the latteroutputs a point-of-origin signal. It is, however, to be noted that wherethe magnetic detecting member 9 has a characteristic reverse to thatdescribed above, the magnetic polarity of the to-be-detected member 8must be correspondingly reverse to that described above. As a magnetforming the to-be-detected member 8, for example, a rubber magnet,plastic magnet or sintered magnet can be conveniently employed. Also, asa magnetic material for the magnet, ferrite, Nd or SmCo material can besuitably employed.

The magnetic detecting member 9 referred to above is in the form of amagnetic sensor such as, for example, a Hall element, Hall IC or MRsensor and is embedded in a annular sensor housing 12 of a generallyU-shaped section. More specifically, the magnetic detecting member 9 canbe embedded in the sensor housing 12 by means of a molding process, inwhich after the magnetic detecting member 9 has been inserted into thesensor housing 12 together with an electric connecting cable (not shown)a resin molding 13 is formed inside the sensor housing 12.

The sensor housing 12 may be made of either a synthetic resin or anon-magnetic metallic material and is fixedly mounted on the stationaryraceway member 5. More specifically, this sensor housing 12 with themagnetic detecting member 9 embedded therein is press-fitted onto anouter peripheral surface of a tubular extension 5 b that is integralwith and extends axially outwardly from one of opposite ends of thestationary raceway member 5 adjacent the right sealing member 7, i.e.,the right end of the stationary raceway member 5 so far shown in FIG. 1.It is, however, to be noted that in such case the electric connectingcable may be dispensed with and, instead, interfacing between themagnetic detecting member 9 and an external circuit element, includingthe supply of an electric power from the external circuit element to themagnetic detecting member 9 and transmission of signals between theexternal circuit element and the magnetic detecting member 9, may becarried out on a non-contact basis (i.e., wireless).

In the combined sensor and bearing assembly 1 of the structure describedabove, the rotation sensor unit 31 provides a point-of-origin signal inthe form of a single pulse from the magnetic detecting member 9 eachtime the rotatable raceway member 4 undergoes one complete rotationabout the longitudinal axis of the bearing assembly 1. With thispoint-of-origin signal, the number of revolutions and the rotationalspeed of the rotatable raceway member 4 can be detected and, therefore,the combined sensor and bearing assembly 1 can be used at any site fromwhich the status of rotation is desired to be detected for the purposeof, for example, detecting a locked condition of a rotary shaft.

FIG. 3 illustrates the use of the combined sensor and bearing assembly 1in a rotary support of the electromagnetic clutch 2. In the instance asshown therein, the electromagnetic clutch 2 is of a kind used to controlthe mechanical coupling and decoupling in a drive system for acompressor incorporated in an automobile air conditioning system. Theillustrated electromagnetic clutch 2 includes an annular stator 14, anannular rotor 15 and an annular clutch plate 16. The rotor 15 isrotatably mounted on and supported by an annular axial protrusion 19 athrough the combined sensor and bearing assembly 1, which protrusion 19a is formed integrally with or otherwise connected rigidly with acompressor housing 19 so as to extend in a direction axially of thebearing assembly 1. The rotatable raceway member 4, which is the outerrace of the combined sensor and bearing assembly 1, is inserted into abore of the rotor 15 of the electromagnetic clutch 2 and is rigidlysecured thereto for rotation together with the rotor 15. On the otherhand, the stationary raceway member 5, which is the inner race of thecombined sensor and bearing assembly 1, is fixedly mounted on theannular axial protrusion 19 a fast with the compressor housing 19.

A pulley 18 is press-fitted onto an outer periphery of the rotor 15 forrotation together therewith and is drivingly coupled with an automotiveengine (not shown) through a substantially endless drive belt so thatrevolution of the automotive engine can be transmitted to the pulley 18and, hence, to the rotor 15. This rotor 15 is of a generally U-sectionedannular configuration having a circumferentially extending inner groove15 a. The stator 14 has an electromagnetic coil 17 built therein and isfixed to the compressor housing 19 so as to protrude loosely into theinner groove 15 a of the rotor 15. Positioned inside the annular axialprotrusion 19 a fast with the compressor housing 19 is a rotary shaft 20of the compressor having a generally L-sectioned flange member 22rigidly secured thereto by means of a bolt 21. The annular clutch plate16 referred to hereinbefore and made of a magnetic material is coupledwith, and positioned radially outwardly of, the flange member 22 througha spring plate 23.

The clutch plate 16 is arranged in face-to-face relation with the rotor15 and, accordingly, when the electromagnetic clutch 2 is electricallyactivated (i.e., powered on), an electric current flow through theelectromagnetic coil 17 with an electromagnetic force of attractiongenerated consequently from the electromagnetic coil 17. Because of thiselectromagnetic force of attraction, the clutch plate 16 is magneticallyattracted by the rotor 15 and, therefore, rotation of the rotor 15caused by the automotive engine through the drive belt by way of thepulley 18 can be transmitted to the rotary shaft 20 of the compressor tothereby drive the compressor. So long as the electromagnetic clutch 2 isdeactivated (i.e., powered off), no rotation of the rotor 15 will not betransmitted to the rotary shaft 20 since the clutch plate 16 isseparated from the rotor 15.

FIG. 4 illustrates the condition of the electromagnetic clutch 2 whenthe latter is activated. As shown therein, upon activation of theelectromagnetic clutch 2, a magnetic circuit as shown by the doubledotted line can be formed. At this time, a leakage magnetic flux flowstowards the combined sensor and bearing assembly. The direction oforientation of the magnetic circuit formed within the stator 14 and therotor 15 of the electromagnetic clutch 2 varies depending on thedirection of flow of the electric current through the electromagneticcoil 17 accommodated within the stator 14. By way of example, assumingthat the magnetic circuit extends in a direction shown by the arrow A inFIG. 4, a magnetic circuit B oriented in the same direction as shown bythe arrow A is also formed in the rotatable raceway member 4 of thecombined sensor and bearing assembly 1. Accordingly, if a Hall IC of aswitching type is employed for the magnetic detecting member 9 and, onthe other hand, the leakage magnetic flux of an intensity higher thanthe sensitivity of the Hall IC flows in a direction shown by the arrowC, the magnetic detecting member 9 can be switched on. In such case,since the magnetic detecting member 9 is kept switched on and is notswitched off even though the to-be-detected member 8 does not confrontthe magnetic detecting member 9, the point of origin cannot be detected.

In view of the above, in the illustrated embodiment, in order to renderthe direction of the magnetic flux, with which the magnetic detectingmember 9 is switched off, to coincide with the direction of the leakagemagnetic flux, the electric current is supplied to the electromagneticcoil 17 so as to flow in a direction reverse to that discussed above asshown in FIG. 5. Accordingly, the direction of orientation of themagnetic circuit formed within the stator 14 and the rotor 15 of theelectromagnetic clutch 2 is such as shown by A′ and the magnetic circuitB′ in the same direction as that shown by A′ is also formed within therotatable raceway member 4. Also, the leakage magnetic flux flows intothe magnetic detecting member 9 as well and this leakage magnetic fluxis oriented in a direction C′ which is in the substantially samedirection as that shown by A′. In such case, the leakage magnetic fluxflowing in the direction C′ causes the Hall IC, forming the magneticdetecting member 9, to be switched off, but when the to-be-detectedmember 8 is brought to a position aligned with the magnetic detectingmember 9, the Hall IC (that is, the magnetic detecting member 9) isnecessarily switched on and, accordingly, the detection of the point oforigin is possible. In other words, the rotation sensor unit 31 iscapable of accomplishing the point-of-origin detection accuratelywithout being adversely affected by the leakage magnetic flux even underthe environment where the leakage magnetic flux exists.

FIG. 6 illustrates a second preferred embodiment of the presentinvention. The combined sensor and bearing assembly 1 shown thereinmakes use of the rotation sensor unit 31 of a radial type, in which theto-be-detected member 8 and the magnetic detecting member 9 confrontwith each other in a radial direction perpendicular to the longitudinalaxis of the bearing assembly 1. In this embodiment, the to-be-detectedmember 8 of the rotation sensor unit 31 is in the form of a magnetmagnetized in an inner peripheral surface of a ring-shaped core metal33, which is in turn press-fitted into a bore of a tubular extension 4 bthat is integral with and extends axially outwardly from one of oppositeends, i.e., a right end, of the rotatable raceway member 4 adjacent theright sealing member 7. The magnet forming the to-be-detected member 8is so magnetized in a radial direction.

On the other hand, the magnetic detecting member 9 is in the form of amagnetic sensor embedded in the annular sensor housing 12 of thegenerally U-shaped section as is the case with that in the embodimentshown in and described with reference to FIGS. 1 to 5, but is positionedin an outer peripheral portion of the sensor housing 12 so that themagnetic detecting member 9 can confronts the to-be-detected member 8 ina direction radially with respect to the longitudinal axis of thebearing assembly 1. Accordingly, the direction in which the magneticdetecting member 9 detects the magnetic field is oriented in a directionD radially of the combined sensor and bearing assembly 1.

The combined sensor and bearing assembly 1 according to this secondembodiment can be equally employed in the electromagnetic clutch 2 shownin FIG. 3 in place of the combined sensor and bearing assembly 1 shownin FIG. 1. Other structural features of the combined sensor and bearingassembly 1 shown in FIG. 6 than those described above are substantiallysimilar to those shown in and described with reference to FIGS. 1 to 5and, therefore, the details thereof are not reiterated for the sake ofbrevity.

According to the second embodiment, while the magnetic circuitestablished within the rotatable raceway member 4 upon activation of theelectromagnetic clutch 2 extends, for example, in a direction shown bythe arrow B and the leakage magnetic flux leaking into the magneticdetecting member 9 flows in the same direction as that shown by thearrow B, the direction in which the magnetic detecting member 9 detectsthe magnetic field in this second embodiment is oriented in the radialdirection D as hereinbefore described. For this reason, the direction ofthe leakage flux and the direction in which the magnetic detectingmember 9 detects cross to each other at an angle of, for example,substantially 90°.

Accordingly, it is possible to accomplish an accurate detection of thepoint of origin without the magnetic detecting member 9 being adverselyaffected by the leakage magnetic flux. Since in the illustratedinstance, the direction of the leakage magnetic flux and the directionin which the magnetic detecting member 9 detects is set to cross to eachother at an angle of substantially 90°, it is possible to substantiallyeliminate the influence which the leakage magnetic flux may bring on themagnetic detecting member 9, allowing the rotation sensor unit 31 toaccomplish an accurate detection of the point of origin.

Also, with this embodiment, similar effects can be obtained regardlessof the direction in which the electric current flows through theelectromagnetic coil 17 of the electromagnetic clutch 2. In addition,since the rotation sensor unit 31 is so designed and so tailored as tobe the radial type as hereinbefore described, it is quite easy to setthe direction, in which the magnetic detecting member 9 detects themagnetic field, to cross relative to the direction of the leakagemagnetic flux emanating from the electromagnetic clutch 2.

Referring now to FIG. 7 showing a third preferred embodiment of thepresent invention, the combined sensor and bearing assembly 1 showntherein is substantially similar to that shown in and described inconnection with the previous embodiment with reference to FIG. 6, exceptthat in accordance with this third embodiment the sensor housing 12 madeof a non-magnetic material and having the magnetic detecting member 9embedded therein as hereinbefore described is fixedly mounted on thetubular extension 5 b through a generally L-sectioned ring member 24made of a magnetic material. Specifically, this L-sectioned ring member24 is press fitted onto the outer peripheral surface of the tubularextension 5 b from the stationary raceway member 5 to allow the magneticdetecting member 9 to be set by the stationary raceway member 5 throughsuch ring member 24. This ring member 24 has a cylindrical body,press-fitted to the tubular extension 5 b, and a radial wall 24 aextending radially outwardly from an inner end of the cylindrical bodyand, in an assembled condition as shown, the radial wall 24 a is held inthe vicinity of the right sealing member 7 so as to extend parallel tothe reinforcement ring 11 of the right sealing member 7. Thereinforcement ring 11 is made of a magnetic material.

Other structural features of the combined sensor and bearing assembly 1shown in FIG. 7 than those described above are substantially similar tothose shown in and described with reference to FIG. 6 and, therefore,the details thereof are not reiterated for the sake of brevity.

According to the third embodiment, since the leakage magnetic flux flowsin the L-sectioned ring member 24 after having bypassed, the leakagemagnetic field can easily flow in a radial direction between therotatable raceway member 4 and the stationary raceway member 5 and,therefore, the leakage magnetic flux D in the radial direction that isinputted to the magnetic detecting member 9 can advantageously bereduced. For this reason, it is possible to avoid an erroneous operationwhich would otherwise occur as a result of influences brought about bythe leakage magnetic flux on the magnetic detecting member 9, allowingan accurate detection of the point of origin to be achieved.

FIG. 8 illustrates a fourth preferred embodiment of the presentinvention. The combined sensor and bearing assembly 1 according to thisfourth embodiment is substantially similar to that shown in anddescribed in connection with the previous embodiment with reference toFIG. 7, except that in place of the L-sectioned ring member 24 used inthe previous embodiment, a bypass ring 25 made of a magnetic material isinterposed between the right sealing member 7 and the sensor housing 12.In this embodiment, the bypass ring 25 is press-fitted onto the outerperipheral surface of the tubular extension 5 b of the stationaryraceway member 5 so as to assume a position in the vicinity of thereinforcement ring 11 of the right sealing member 7 and made of amagnetic material.

According to the fourth embodiment, the magnetic resistance between therotatable raceway member 4 and the stationary raceway member 5 can bereduced by the bypass ring 25, allowing the leakage flux to beconcentrated on the bypass member 25. For this reason, the magnetic fluxleaking around the magnetic detecting member 9 can be reduced and,hence, the accurate detection of the point of origin can advantageouslybe accomplished without the magnetic detecting member 9 being adverselyaffected by the leakage magnetic flux.

A fifth preferred embodiment of the present invention will now bedescribed with particular reference to FIG. 9. The combined sensor andbearing assembly 1 shown in FIG. 9 is substantially similar to thatshown in and described in connection with the previous embodiment withreference to FIG. 8, except that in place of the bypass ring 25 employedin the embodiment of FIG. 8, a generally U-shaped bypass ring 26 formedby splitting an O-ring to have a cutout 26 a is employed. This generallyU-shaped bypass ring 26 is press-fitted on the tubular extension 5 b ofthe stationary raceway member 5 with the to-be-detected member 8 and themagnetic detecting member 9 positioned within the cutout 26 a.

In this fifth embodiment, the to-be-detected member 8 in the form of amagnet is fitted directly to the inner peripheral surface of the tubularextension 4 b of the rotatable raceway member 4 with no core metal 33 ofFIG. 8 employed. Similarly, the magnetic detecting member 9 is fitteddirectly to the outer peripheral surface of the tubular extension 5 b ofthe stationary raceway member 5 with no sensor housing 12 of FIG. 8employed. In such case, the bypass ring 26 is disposed at an axialposition aligned with any one of the to-be-detected member 8 and themagnetic detecting member 9, but alternatively such bypass ring 26 maybe disposed at an axial position displaced from the magnetic detectingmember 9 as is the case with that in the embodiment shown in anddescribed with reference to FIG. 8. Accordingly, so far as the axialposition of the bypass ring 26 is concerned, the bypass ring 26 can havea relatively large freedom of disposition.

It is, however, to be noted that even the bypass ring 26 is positionedin the vicinity of the reinforcement ring 7 of the right sealing member11 as is the case with that in the embodiment of FIG. 8 and that therolling bearing 6 employed in the embodiment of FIG. 9 is substantiallysimilar to that shown in and described with reference to FIG. 8.

Even in the combined sensor and bearing assembly 1 according to thefifth embodiment shown in and described with reference to FIG. 9, thebypass ring 26 made of a magnetic material contributes to reduction ofthe magnetic resistance between the rotatable raceway member 4 and thestationary raceway member 5 to allow the leakage magnetic flux to beconcentrated on the bypass ring 26 and, therefore, it is possible toaccomplish an accurate detection of the point of origin without themagnetic detecting member 9 being adversely affected by the leakagemagnetic flux. In such case, since the bypass ring 26 can be arranged atthe axial position in alignment with the magnetic detecting member 9,the rotation sensor unit 31 can be assembled compact in size.

With particular reference to FIGS. 10 and 11, the combined sensor andbearing assembly 1 according to a sixth preferred embodiment of thepresent invention will now be described. This combined sensor andbearing assembly 1 is substantially similar to that according to thefirst embodiment shown in and described with reference to FIGS. 1 and 2,except that in this embodiment the right sealing member 7 is providedwith an S-pole magnet 8S, which defines the to-be-detected member 8, andan N-pole magnet 8N spaced from the S-pole magnet 8S in a directioncircumferentially of the rotatable and stationary raceway members 4 and5. Those magnets 8S and 8N are specifically spaced 180° from each otherabout the longitudinal axis of, for example, the stationary racewaymember 5. The direction of the magnetic flux required to switch themagnetic detecting member 9 (FIG. 1) off and the direction of theleakage magnetic flux may not be specifically limited.

Other structural features of the combined sensor and bearing assembly 1according to the sixth embodiment than those described above aresubstantially similar to those shown in and described in connection withthe first embodiment with reference to FIGS. 1 and 2 and, therefore, thedetails thereof are not reiterated for the sake of brevity.

According to the sixth embodiment, when the rotatable raceway member 4rotates with no leakage magnetic field developed, the Hall IC used asthe magnetic detecting member 9 provides such an output that as shown bythe waveform (a) in FIG. 11, the Hall IC can be switched on only whenthe magnetic detecting member 9 moves past, i.e., detects the S-polemagnet 8S, and therefore, a normal waveform of one pulse for onecomplete rotation can be obtained.

Where the use is made under the environment in which the leakagemagnetic flux with which the Hall IC can be switched on at all times isapplied as described with reference to FIG. 4, it is possible to switchthe Hall IC off, having overcome the leakage magnetic flux tending toswitch the Hall IC on, when the N-pole magnet 8N then rotating togetherwith the rotatable raceway member 4 approaches the Hall IC. As a result,such an output signal as shown by the waveform (b) in FIG. 11 can beobtained from the magnetic detecting member 9. Although the respectivepulse widths of the waveforms (a) and (b) shown in FIG. 11 differ fromeach other, this difference can be negligible where the combined sensorand bearing assembly 1 is used for detection of the rotational speed ofthe rotatable raceway member 4 or for detection of the presence orabsence of the revolution taking place. As described above, the use ofthe S-pole and N-pole magnets 8S and 8N for the to-be-detected member 8is effective to accomplish the accurate detection of the point of originwithout being adversely affected by the leakage magnetic flux.

The present invention having been fully described, it is to be notedthat in the practice of any one of the previously described embodimentsof the present invention, the magnetic sensor (for example, the Hall IC)used in the magnetic detecting member 9 may be in the form of a magneticsensor of a type having a sensitivity so low that the leakage magneticflux in the vicinity of the magnetic detecting member 9 can not bedetected. Thus, selection of the magnetic sensor of the type having anoperating magnetic flux intensity required for the magnetic detectingmember 9 to be switched on, which is higher than the leakage magneticflux, it is possible to prevent an erroneous operation in the presenceof the leakage magnetic flux, allowing the magnetic detecting member 9to be switched on only when the to-be-detected member 8 is brought to aposition confronting the magnetic detecting member 9. In the case ofthis arrangement, the influence brought about by the leakage magneticflux on the magnetic detecting member 9 can advantageously be minimized,regardless of the relation between the direction, in which the magneticdetecting member 9 detects the magnetic field, and the direction of theleakage magnetic flux.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings which are used only for the purpose ofillustration, those skilled in the art will readily conceive numerouschanges and modifications within the framework of obviousness upon thereading of the specification herein presented of the present invention.By way of example, although in describing any of the foregoingembodiments of the present invention the outer and inner races have beenshown and described as represented by the rotatable and stationaryraceway members 4 and 5, respectively, the present invention can beequally applied even where the rotatable and stationary raceway members4 and 5 represent the inner and outer races, respectively.

Also, the combined sensor and bearing assembly of the present inventioncan be used not only in association with the electromagnetic clutch suchas shown and described, but in the vicinity of any coil from which aleakage magnetic flux emanates such as, for example, a coil of anelectric drive motor.

Accordingly, such changes and modifications are, unless they depart fromthe scope of the present invention as delivered from the claims annexedhereto, to be construed as included therein.

1. A combined sensor and bearing assembly having a capability ofdetecting a point of origin, the assembly comprising: a rolling bearingunit made up of a rotatable raceway member, a stationary raceway memberand at least one row of rolling elements rollingly interposed betweenthe rotatable and stationary raceway members; and a rotation sensor unitincluding a to-be-detected member made up of a magnet fitted to one ofthe raceway members; and a magnetic detecting member fitted to the otherraceway member at a location confronting the to-be-detected member,wherein the combined sensor and bearing assembly is used at a locationclose to an electric coil emanating a leakage magnetic field in acondition in which a direction of flow of an electric current throughthe coil is fixed in one direction; and the magnet of the to-be-detectedmember is made up of a first magnet of which an S-pole is to bedetected, and a second magnet of which an N-pole is to be detected andspaced from the first magnet in a direction circumferentially of therotatable and stationary raceway members.